Characterization of phenolic compounds from Rhododendron alutaceum

Article abstract of DOI:10.1007/s12272-012-1104-9

A new phenolic glycoside, 3′-keto rhododendrin (1) and a new sesquilignan, alutaceuol (2), together with twelve known phenolic compounds, were isolated from the leaves of Rhododendron alutaceum. Their structures were elucidated by extensive spectroscopic data analysis and comparison with literature values. In addition, the detailed analysis of 2D NMR data led us to conclude that the chemical shifts of dihydrobuddlenol B (5) need to be revised.

Full text of DOI:10.1007/s12272-012-1104-9

Arch Pharm Res Vol 35, No 11, 1887-1893, 2012
DOI 10.1007/s12272-012-1104-9
Characterization of Phenolic Compounds from Rhododendron aluta-
ceum
Hai-Zhou Li, He-Jiao Song, Hong-Mei Li, Yu-Yin Pan, and Rong-Tao Li
Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming 650500, China
(Received October 21, 2011/Revised June 14, 2012/Accepted June 17, 2012)
A new phenolic glycoside, 3'-keto rhododendrin (1) and a new sesquilignan, alutaceuol (2),
together with twelve known phenolic compounds, were isolated from the leaves of Rhododen-
dron alutaceum. Their structures were elucidated by extensive spectroscopic data analysis and
comparison with literature values. In addition, the detailed analysis of 2D NMR data led us to
conclude that the chemical shifts of dihydrobuddlenol B (5) need to be revised.
Key words: Rhododendron alutaceum, Ericaceae, 3'-Keto rhododendrin, Alutaceuol
with the 2D NMR data.
INTRODUCTION
Many species of the genus Rhododendron which
belongs to the family Ericaceae are famous ornamen-
tal flowers and have been used as Chinese traditional
medicine with anti-inflammatory, antitussive and anti-
MATERIALS AND METHODS
General experimental procedures
Optical rotation was measured with a JascoDIP-370
pyretic activities (Flora of China Editorial Committee, digital polarimeter. 1D and 2D NMR spectra were re-
2005). Rhododendron alutaceum Balf. F., a shrub only corded using Bruker AM-400 and DRX-500 instru-
growing in the high mountain forest of southwest ments with tetramethylsilane (TMS) as an internal
China, is used as herbal medicine for relieving cough standard. FAB-MS was measured on a VG Auto Spec-
and eliminating phlegm (Jiangsu New Medical College, 3000 spectrometer, and HR-ESI-MS was taken on an
1986). So far, there is no report on the phytochemical API Qstar Pulsar instrument. Semipreparative HPLC
investigation of this plant. In a systematic study on was performed on an Agilent 1200 liquid chromato-
chemical constituents of species in different genera graph with a ZORBAX SB-C18 (5 µm, 9.4 × 250 mm)
belonging to the family Ericaceae (Wang et al., 2010a, column. Column chromatography (CC) was carried out
2010b; Wu et al., 2011), two new phenolic compounds, on silica gel (80-100 mesh, 100-200 mesh and 200-300
3'-keto rhododendrin (
three known 4-(4-hydroxyphenyl)-2-butanol deriva- RP-18 (43-63
tives, four known lignans and five known flavonoids, Biosciences AB) and MCI (MCI-gel CHP-20P, 75-150
were isolated from the leaves of R. alutaceum. Herein, m, Mitsubishi Chemical Corporation). Fractions were
1) and alutaceuol (2
), along with mesh, Qingdao Marine Chemical Factory), Lichroprep®
µm, Merck), Sephadex LH-20 (Amersham
µ
details of the isolation and structural elucidation of monitored by TLC plates (Si gel GF254, Qingdao Marine
these two new compounds are presented. Moreover, Chemical Factory), and visualized by heating after
through the extensive analyzing 2D NMR spectra, the having sprayed with 5% H2SO4-EtOH.
chemical shifts of the previously reported dihydrobud-
dlenol B (5), which was elucidated on the basis of 1D
Plant material
NMR data, need to be revised for being consistent
The sample of R. alutaceum was collected from Cang
Montain, Dali, Yunnan Province, P. R. China, in August
2008, and was identified by Dr. Yong-Peng Ma, Kun-
ming Institute of Botany, Chinese Academy of Sciences.
A voucher specimen (KMUST 20080001) was deposited
at the Laboratory of Phytochemistry, Kunming Uni-
Correspondence to: Rong-Tao Li, Faculty of Life Science and Tech-
nology, Kunming University of Science and Technology (Cheng-
gong Campus), Kunming 650500, China
Tel: 86-871-5920657, Fax: 86-871-5920570
E-mail: rongtaolikm@yahoo.cn
1887

1888
H.-Z. Li et al.
versity of Science and Technology.
the EtOAc layer was further purified by Sephadex
LH-20 (40-100% MeOH in H2O) to yield (-)-rhododen-
16.7o, c = 0.3, CH3OH), which
22
drol (
4
) (2.4 mg, [α D
]
=
−
Extraction and isolation
1
Air-dried leaves (4 kg) of R. alutaceum were powder- was identified by H-NMR data and negative optical
ed and extracted with 75% Me2CO/H2O (2×25 L, 2d, rotation.
each) at room temperature and filtered. The filtrate
was concentrated in vacuo and the resulting residue Alutaceuol (2)
was extracted with petroleum ether and EtOAc, re- Amorphous powder. [α D
4.56o (
c
= 0.5, CH3OH);
22
]
=
−
spectively.
CD (c = 0.29, MeOH) (mdeg): 205 (+9.68), 209 (-9.41).
The EtOAc extract (75 g) was chromatographed over FAB−-MS: m/z 571 [M-H]−; HR-ESI-MS ([M-H]−,
Sephadex LH-20, eluting with 30%, 60%, 90% MeOH- C30H35O11−, found 571.2171, calcd. 571.2179). IR (KBr)
H2O to afford fractions I-IV. Fraction II (6 g) was sub- cm−1: 3435, 1610, 1508, 1040. 1H- and 13C-NMR spectral
jected to MCI gel column (eluted with 30%, 60%, and data: see Table I.
90% MeOH-H2O) to give four fractions (fr. 2.1-fr. 2.4).
Fraction 2.1 was further purified by repeated on silica Rhododendrin (3)
22
gel column (CH3Cl-MeOH 10:1) and yielded compounds Amorphous powder. [α D
]
=
−
33.85o (
c
= 0.88, CH3OH);
7.24 (1H, d,
= 8.4 Hz, H-3, 5), 2.79
(MeOH-H2O 2:3) and HPLC (MeOH-H2O 1:1) repeat- (2H, m, H-7), 1.75 (2H, m, H-8), 3.59 (1H, m, H-9),
edly, to obtain compounds (7 mg), (7 mg), (6 mg) 1.24 (3H, d, = 6.1 Hz, H-10), 4.90 (1H, d, = 7.7 Hz,
and
(5 mg). Compound 10 (15 mg) was purified from H-1'), 3.90-4.6 (5H, H-2'- H-5'). 13C-NMR (CD3COCD3,
fraction 2.3 by RP-18 (eluted with MeOH-H2O 1:4) 100 MHz): 133.4 (s, C-1), 130.2 (d, C-2, 6), 116.2 (d,
1
(10 mg) and
3
(15 mg). Fraction 2.2 was chromato- 1H-NMR (CD3COCD3, 400 MHz ):
δ
J =
graphed over silica gel (CH3Cl-MeOH 10:1), RP-18 8.4 Hz, H-2, 6), 7.16 (1H, d,
J
2
5
8
J
J
9
δ
and Sephadex LH-20 (eluted with 30%, 60%, 90% C-3, 5), 157.0 (s, C-4), 31.3 (t, C-7), 40.2 (t, C-8), 73.6
MeOH-H2O). After repeated silica gel column chroma- (d, C-9), 20.2 (q, C-10), 102.5 (s, C-1'), 75.3 (d, C-2'),
tography (petroleum ether/Me2CO 9:1 and petroleum 78.7 (d, C-3'), 71.8 (d, C-4'), 78.5 (d, C-5'), 62.9 (t, C-6').
ether/EtOAc 4:1, respectively), fraction 2.4 afforded
(11 mg) and (10 mg). Fraction III (12 g) was subjected
to MCI gel (30%, 60%, and 90% MeOH-H2O), Sephadex Amorphous powder. [
LH-20 (30%, 60%, 90% MeOH-H2O) and RP-18 (10%- 1H-NMR (CD3COCD3, 400 MHz):
60% MeOH eluate) to give compounds 11 (15 mg), 12 Hz, H-10), 3.76 (1H, m, H-9), 1.64 (2H, m, H-8), 2.60
4
7
(−)-Rhododendrol (4)
22
α]
=
−
16.68o (
1.16 (3H, d,
c
= 0.44, CH3OH);
= 6.1
D
δ
J
(20 mg), 13 (30 mg), 14 (13 mg) and 15 (15 mg).
(2H, m, H-7), 7.02 (2H, d,
d,
= 8.3 Hz, H-3, 5); 13C-NMR (CD3COCD3, 100
MHz): 133.9 (s, C-1), 129.9 (d, C-2, 6), 115.8 (d, C-3,
J = 8.3 Hz, H-2, 6), 6.74 (2H,
J
δ
3'-Keto rhododendrin (1)
22
Amorphous powder. [α D
]
=
−
29.58o (
c
= 0.46, CH3OH); 5), 156.0 (s, C-4) , 31.8 (t, C-7) , 42.2 (t, C-8), 67.0 (d,
FAB−-MS: m/z 325 [M-H]−; HR-ESI-MS ([M-H]−, C-9), 23.9 (q, C-10).
C16H21O7−, found 325.1285, calcd. 325.1287). IR (KBr)
1
1
cm− : 3645, 1710, 1610, 1498, 1045. H-NMR (500 Dihydrobuddlenol B (5)
MHz, CD3OD):
(2H, d,
= 8.4 Hz, H-3, 5), 1.70 (1H, m, H-7a), 1.87 (KBr) cm−1: 3435, 1610, 1509. 1H- and 13C-NMR spec-
(1H, m, H-7b), 2.64 (2H, m, H-8), 3.93 (1H, m, H-9), tral data: see Table I.
1.19 (3H, d, = 6.4 Hz, H-10), 4.43 (1H, d, = 7.8 Hz,
H-1'), 4.11 (1H, d, = 7.8 Hz, H-2'), 4.25 (1H, d,
1.6 Hz, H-4'), 3.30 (1H, m, H-5'), 3.93 (1H, dd, = 2.0, Amorphous powder. [
12.0 Hz, H-6'a), 3.83 (1H, dd,
= 4.4, 12.0 Hz, H- 1H-NMR (CD3COCD3, 400 MHz):
6'b).13C-NMR (125 MHz, CD3OD)
: 134.5 (C-1), 130.1 2), 6.47 (1H, d, = 7.8 Hz, H-5), 6.29 (1H, d,
(C-2, 6), 116.2 (C-3, 5), 156.3 (C-4), 31.8 (C-7), 40.5 (C- Hz, H-6), 2.50 (2H, m, H-7), 1.64 (2H, m, H-8), 3.70
8), 75.7 (C-9), 20.0 (C-10), 103.8 (C-1'), 78.1 (C-2'), (1H, m, H-9), 1.11 (3H, d,
= 6.0 Hz, H-10); 13C-NMR
135.0 (s, C-1), 116.2 (d, C-2),
δ 7.04 (2H, d, J
= 8.4 Hz, H-2, 6), 6.67 Amorphous powder. FAB−-MS: m/z 585 [M-H]−. IR
J
J
J
J
J
=
(−)-Rhodolatouchol (7)
18.20o (
6.49 (1H, br s, H-
= 7.8
c = 0.44, CH3OH);
22
J
α]
=
−
D
J
δ
δ
J
J
J
207.3 (C-3'), 73.6 (C-4'), 78.3 (C-5'), 62.5 (C-6').
(CD3COCD3, 100 MHz): δ
143.7 (s, C-3), 145.7 (s, C-4), 115.9 (d, C-5), 120.2 (d, C-6),
32.1 (t, C-7) , 42.3 (t, C-8), 66.9 (d, C-9) , 23.9 (q, C-10).
Acid hydrolysis of 1
A solution of
1 (7 mg) in 1 M HCl (1 mL) was heated
at 90-100°C in a screw-capped vial for 5 hours. The Ficusequilignan A (8)
mixture was partitioned between EtOAc (1 mL), and Amorphous powder. FAB−-MS: m/z 585 [M-H]−, 1H-

Phenolic Compounds from R. alutaceum
1889
NMR (CD3OD, 400 MHz):
δ
6.65 (s, H-2,6), 4.75 (d,
J
(s, C-3''), 146.8 (s, C-4''), 115.6 (d, C-5''), 120.7 (d, C-6''),
= 3.2 Hz, H-7), 3.13 (m, Hz, H-8), 3.89, 4.28 (m, H-9), 74.0 (d, C-7''), 87.5 (d, C-8''), 61.6 (t, C-9'').
6.91 (d, = 1.9 Hz, H-2'), 6.90 (d, = 8.1 Hz, H-5'), 6.91
(dd, = 8.0, 1.9 Hz, H-6'), 4.70 (d, = 4.4 Hz, H-7'), Ehletianol C (9)
3.13 (m, H-8'), 3.89, 4.28 (m, H-9'), 6.96 (s, H-2''), 6.76 Amorphous powder. FAB−-MS: m/z 555 [M-H]−, 1H-
(d, = 8.0 Hz, H-5''), 6.76 (dd, = 8.0, 1.8 Hz, H-6''), NMR (CD3COCD3, 400 MHz): 7.01 (d, = 1.5 Hz, H-
4.90 (t, = 3.4 Hz, H-7''), 4.25 (1H, m, H-8''), 3.89 (1H, 2), 6.74 (d, = 8.0 Hz, H-5), 6.85 (dd, = 8.0, 1.5 Hz,
m, H-9''a), 3.59 (1H, dd, = 6.2 Hz, H-7), 4.24 (dd, = 11.7, 6.75
= 2.7, 12.1 Hz, H-9''b). 13C- H-6), 4.79 (d,
NMR (CD3OD, 100 MHz): 138.9 (s, C-1), 104.2 (d, C- Hz, H-8), 3.71 (dd, = 12.0, 4.0 Hz, H-9a), 3.46 (dd,
2), 154.5 (s, C-3), 136.0 (s, C-4), 154.5 (s, C-5), 104.2 (d, = 12.0, 5.2 Hz, H-9b), 6.87 (d, = 1.5 Hz, H-2'), 6.97 (d,
C-6), 87.3 (d, C-7), 55.3 (d, C-8), 72.7 (t, C-9), 133.7 (s, = 8.0 Hz, H-5'), 6.71 (dd, = 8.0, 1.5 Hz, H-6'), 2.95
C-1'), 110.9 (d, C-2'), 148.9 (s, C-3'), 147.3 (s, C-4'), (dd, = 13.0, 5.0 Hz, H-7'), 2.72 (m, H-8'), 3.97 (1H,
116.0 (d, C-5'), 120.1 (d, C-6'), 87.3 (d, C-7'), 55.7 (d, C- dd, = 8.0, 10.2 Hz, H-9'a), 3.67 (1H, dd, = 8.0, 10.2
= 1.5 Hz, H-2''), 6.75 (d, = 8.0
= 8.0, 1.5 Hz, H-6''), 4.74 (dd,
= 8.5 Hz, H-8''), 3.82
=11.0, 8.0 Hz, H-9''a), 3.63 (dd, =11.0, 8.0 Hz,
H-9''b). 13C-NMR (CD3COCD3, 100 MHz):
134.3 (s,
J
J
J
J
J
J
δ
J
J
J
J
J
J
J
δ
J
J
J
J
J
J
J
J
8'), 72.9 (t, C-9'), 133.7 (s, C-1''), 111.3 (d, C-2''), 148.5 Hz, H-9'b), 6.90 (d,
Hz, H-5''), 6.76 (dd,
J
J
J
J
= 6.8, 1.0 Hz, H-7''), 2.33 (1H, t,
(dd,
J
Table I. 1H- and 13C-NMR Data of
2
and
5
(500 MHz for
1H and 125 MHz for 13C, CD3OD)
J
J
δ
2
5
C-1), 111.3 (d, C-2), 147.9 (s, C-3), 146.6 (s, C-4), 113.9
(d, C-5), 120.5 (d, C-6), 73.0 (d, C-7), 86.9 (d, C-8), 61.8
(t, C-9), 136.5 (s, C-1'), 113.8 (d, C-2'), 151.8 (s, C-3'),
147.9 (s, C-4'), 119.2 (d, C-5'), 121.7 (d, C-6'), 33.5 (t, C-
7'), 43.3 (d, C-8'), 73.7 (t, C-9'), 134.3 (s, C-1''), 110.6 (d,
C-2''), 148.1 (s, C-3''), 147.1 (s, C-4''), 115.3 (d, C-5''),
119.7 (d, C-6''), 83.2 (d, C-7''), 53.9 (d, C-8''), 60.3 (t, C-
9'').
No.
13C
1H
13C
1H
2
3
3a
88.2 5.55 (dd, 2.1, 5.6) 88.0 5.56 (d, 6.5)
56.0 3.43 (m)
65.2 3.86 (m)
3.75 (m)
116.7 6.59 (s)
129.3 -
55.1 3.43 (m)
64.7 3.81 (m)
3.75 (m)
117.5 6.82 (s)
129.6 -
136.5 -
4
4a
5
137.0 -
5a
5b
5c
6
7
7a
1'
2'
3'
4'
5'
32.7 2.56 (t, 8.0)
35. 8 1.78 (m)
62.3 3.54 (m)
117.1 6.58 (s)
141.9 -
146.8 -
140.0 -
103.8 6.75 (s)
154.5 -
136.1 -
154.5 -
103.8 6.75 (s)
133.8 -
111.3 6.96 (d, 2.0)
148.6 -
146.4 -
115.7 6.72 (d, 8.0)
120.6 6.77 (dd, 2.0, 8.0) 119.9 6.83 (dd, 2.0, 8.0)
74.0 4.89 (d, 4.9)
87.4 4.23 (m)
61.6 3.87 (m)
3.54 (m)
32.6 2.56 (t, 7.7)
35.9 1.77 (m)
61.8 3.54 (m)
113.9 6.81 (s)
144.9 -
147.1 -
139.3 -
104.0 6.73 (s)
154.2 -
135.9 -
154.2 -
104.0 6.73 (s)
133.7 -
110.7 7.02 (d, 2.0)
147.9 -
146.4 -
2,3-Dihydrobenzofuran-2-(4'-hydroxy-3'-methoxy-
phenyl)-3-
oxy-5-propanol (10)
α-L-rhamnopyranosyloxymethyl-7-meth-
1
Amorphous powder. H-NMR (CD3OD, 400 MHz):
1.18 (3H, d, = 6.4 Hz, H-6''), 1.80 (2H, m, H-8'), 2.66
(2H, t, = 7.4 Hz, H-9'), 4.75 (1H, d, = 1.2 Hz, H-1''),
3.33-3.83 (4H, m, H-2''-5''), 3.65 (1H, m, H-8), 3.59 (2H,
m, H-7'), 3.65 (1H, dd, = 6.0, 12.0 Hz, H-9a), 3.84 (3H,
s, -OCH3), 3.85 (3H, s, -OCH3), 4.00 (1H, dd, = 6.0,
12.0 Hz, H-9b), 5.47 (1H, d, = 6.9 Hz, H-7), 6.79 (1H,
d, = 2.0 Hz, H-2'), 6.72 (1H, d, = 2.0 Hz, H-6'), 6.81
(1H, d, = 2.0 Hz, H-2), 7.01 (1H, d, = 8.0 Hz, H-5),
6.87 (1H, dd,
= 2.0, 8.0 Hz, H-6). 13C-NMR (CD3OD,
100 MHz): 134.1 (s, C-1), 119.4 (d, C-2), 147.1 (s, C-
δ
J
J
J
J
J
J
J
J
6'
J
J
1''
2''
3''
4''
5''
6''
7''
8''
9''
J
δ
3), 144.8 (s, C-4), 117.2 (d, C-5), 115.6 (d, C-6), 88.6 (d,
C-7), 52.2 (d, C-8), 69.5 (t, C-9), 129.0 (s, C-1'), 110.2
(d, C-2'), 147.1 (s, C-3'), 144.8 (s, C-4'), 136.3 (d, C-5'),
113.8 (d, C-6'), 35.6 (t, C-7'), 32.5 (t, C-8'), 61.6 (t, C-9'),
101.0 (s, C-1''), 71.8 (d, C-2''), 72.3 (s, C-3''), 73.5 (s, C-
4''), 69.9 (d, C-5''), 18.1 (d, C-6'').
115.2 6.75 (d, 8.0)
73.3 4.97 (d, 4.9)
87.8 4.19 (m)
60.8 3.91 (m)
3.52 (m)
56.5 3.82 (s)
56.5 3.82 (s)
56.1 3.84 (s)
56.4 3.81 (s)
Quercetin 3-
Amorphous powder. 1H-NMR (DMSO-d6, 400 MHz):
6.19 (1H, d, = 1.9 Hz, H-6), 6.39 (1H, d, = 1.9 Hz,
H-8), 7.51 (1H, d, = 2.1 Hz, H-2'), 6.80 (1H, d, = 8.5
Hz, H-5'), 7.65 (1H, dd, = 2.1, 8.3 Hz, H-6'), 5.36 (1H,
O-β-D-galactopyranoside (11)
3'-OMe
5'-OMe
3''-OMe
7-OMe
56.6 3.79 (s)
56.6 3.79 (s)
56.3 3.82 (s)
δ
J
J
J
J
-
-
J

1890
H.-Z. Li et al.
d,
J
= 7.7 Hz, H-1''), 3.15-3.63 (5H, m, H-2''~6''), 12.63 164.8 (s, C-5), 96.8 (d, C-6), 168.2 (s, C-7), 95.9 (d, C-
(1H, s, 5-OH); 13C-NMR (DMSO-d6, 100 MHz):
δ 156.3 8), 163.8 (s, C-9), 101.3 (s, C-10), 128.1 (s, C-1'), 107.9
(s, C-2), 133.5 (s, C-3), 177.5 (s, C-4), 161.3 (s, C-5), (d, C-2'), 146.5 (s, C-3'), 134.2 (s, C-4'), 146.5 (s, C-5'),
98.7 (d, C-6), 164.1 (s, C-7), 93.5 (d, C-8), 156.2 (s, C- 107.9 (d, C-6').
9), 103.9 (s, C-10), 121.1 (s, C-1'), 115.2 (d, C-2'), 144.8
(s, C-3'), 148.5 (s, C-4'), 115.9 (d, C-5'), 122.0 (d, C-6'),
101.8 (d, C-1''), 71.2 (d, C-2''), 73.2 (d, C-3''), 67.9 (d, C-
4''), 75.9 (d, C-5''), 60.1 (t, C-6'').
RESULTS AND DISCUSSION
The EtOAc-soluble fraction of the 75% aq. acetone
extract from the leaves of R. alutaceum was repeated-
ly chromatographed with various solvent systems on
normal and reversed-phase columns, Sephadex LH-20
Quercetin 3-
Amorphous powder. 1H-NMR (DMSO-d6, 400 MHz):
6.19 (1H, d, = 1.8 Hz, H-6), 6.39 (1H, d,
H-8), 7.46 (1H, d, = 2.2 Hz, H-2'), 6.84 (1H, d,
Hz, H-5'), 7.54 (1H, dd, = 2.1, 8.5 Hz, H-6'), 5.57 (1H, sesquilignan, alutaceuol (
s, H-Ara-1), 4.14-3.29 (6H, m, H-Ara-2~6), 12.64 (1H, phenolic compounds.
s, 5-OH); 13C-NMR (DMSO-d6, 100 MHz):
156.9 (s, Compound was obtained as an amorphous powder
O-α-L-arabinofuranoside (12)
δ
J
J
= 1.8 Hz, as well as C-18 semipreparative HPLC to afford a new
= 8.5 phenolic glycoside, 3'-keto rhododendrin ( ), and a new
), together with 12 known
J
J
1
J
2
δ
1
22
C-2), 133.4 (s, C-3), 177.7 (s, C-4), 161.2 (s, C-5), 98.7 (d, with negative optical rotation ([
α]
= −
29.58o). A
D
C-6), 164.2 (s, C-7), 93.6 (d, C-8), 156.3 (s, C-9), 103.9 quasi-molecular ion peak at m/z 325.1285 ([M-H]−) in
(s, C-10), 120.9 (s, C-1'), 115.5 (d, C-2'), 144.8 (s, C-3'), the negative HR-ESI-MS indicated the molecular for-
148.5 (s, C-4'), 115.5 (d, C-5'), 121.7 (d, C-6'), 107.8 (d, mula of C16H22O7, and corresponding to six degrees of
C-1''), 82.1 (d, C-2''), 76.9 (d, C-3''), 85.8 (d, C-4''), 60.6 unsaturation. The IR spectrum showed the absorption
(t, C-5'').
bands of hydroxyl (3465 cm−1), carbonyl (1710 cm−1)
and aromatic (1610, 1498 cm−1) groups.
Quercetin (13)
The 1H- and 13CNMR spectra of
1
exhibited the pres-
-substituted benzene ring [ H 7.04 (2H, d,
C 130.1), 6.67 (2H, d, = 8.4 Hz, H-
= 8.4 3, 5; δC 116.2)], a methyl [δH 1.19 (3H, d, = 6.4 Hz,
= 2.1, 8.4 Hz, H-6'); 13C-NMR H-10);
C 20.0], two methylenes [ H 2.64 (2H, m, H-8),
146.8 (s, C-2), 135.8 (s, C-3), 1.70, 1.87 (each, 1H, m, H-7); δC 40.5, 31.8], an oxy-
H 3.93 (1H, m, H-9); C 75.7], and a
H 4.43 (1H, d, = 7.8 Hz,
= 7.8 Hz, H-2'), 4.25 (1H, d, = 1.6
Hz, H-4'), 3.30 (1H, m, H-5'), 3.93 (1H, dd, = 2.0, 12.0
Hz, H-6'a), 3.83 (1H, dd, = 4.4, 12.0 Hz, H-6'b); δC
103.8 (C-1'), 78.1 (C-2'), 207.3 (C-3'), 73.6 (C-4'), 78.3
Amorphous powder. 1H-NMR (DMSO-d6, 400 MHz):
δ
ence of a
p
δ
J
6.17 (1H, d,
J
= 2.0 Hz, H-6), 6.41 (1H, d,
J
= 2.0 Hz, = 8.4 Hz, H-2, 6;
δ
J
H-8), 7.66 (1H, d,
Hz, H-5'), 7.54 (1H, dd,
(DMSO-d6, 100 MHz):
175.9 (s, C-4), 156.2 (s, C-5), 98.2 (d, C-6), 163.9 (s, C- genated methine [
7), 93.4 (d, C-8), 160.8 (s, C-9), 103.0 (s, C-10), 122.0 (s, ketohexopyranosyl moiety [
C-1'), 115.0 (d, C-2'), 145.1 (s, C-3'), 147.7 (s, C-4'), H-1'), 4.11 (1H, d,
115.6 (d, C-5'), 120.0 (d, C-6').
J
= 2.1 Hz, H-2'), 6.87 (1H, d,
J
J
J
δ
δ
δ
δ
δ
δ
J
J
J
J
J
Catechin (14)
Amorphous powder. 1H-NMR (CD3COCD3, 400 MHz): (C-5'), 62.5 (C-6')].
δ
4.53 (1H, d,
(1H, dd, = 5.0, 16.7 Hz, H-4a), 2.56 (1H, dd,
16.7 Hz, H-4b), 5.83 (1H, d, = 2.3 Hz, H-6), 5.99 (1H, butyl) phenol. The proton and carbon signals of
d, = 2.3 Hz, H-8), 6.92 (1H, d, = 1.9 Hz, H-2'), 6.73 similar to those of rhododendrin ( ) (Das et al., 1993),
(1H, d, = 8.1 Hz, H-5'), 6.70 (1H, dd, = 1.9, 8.1 Hz, except for the signals of sugar moiety. The ketone group
H-6'). 13C-NMR (CD3COCD3, 100 MHz):
82.8 (d, C- in the ketoside was located at C-3', as the evidence
J
= 7.7 Hz, H-2), 4.42 (1H, m, H-3), 2.88
= 8.0, revealed that the aglycone moiety was 4-(3-hydroxy-
were
Analysis of the 1H-1H COSY and HMBC spectra of
1
J
J
J
1
J
J
3
J
J
δ
2), 68.8 (d, C-3), 28.5 (t, C-4), 157.8 (s, C-5), 96.3 (s, C- from the HMBC correlations of the protons H-1', H-2',
6), 156.9 (s, C-7), 95.5 (d, C-8), 157.6 (s, C-9), 99.4 (s, and H-4' with C-3' (δC 207.3) (Fig. 2). Furthermore,
C-10), 131.8 (s, C-1'), 115.4 (d, C-2'), 145.4 (s, C-3'), the HMBC correlation from the anomeric proton (H-
145.5 (s, C-4'), 115.5 (d, C-5'), 118.9 (d, C-6').
1') to C-9 of the aglycone indicated that the ketoside
should be connected to C-9 with -configuration due to
large coupling constant (J1',2' = 7.8 Hz). Acidic hydrol-
ysis of with 1 HCl afforded ( )-rhododendrol (
β
Myricetin (15)
Amorphous powder. 1H-NMR (DMSO-d6, 400 MHz):
δ
1
M
−
4)
22
4.49 (1H, d,
H-3), 5.94 (1H, d,
Hz, H-8), 6.56 (2H, br s, H-2', 6'). 13C-NMR (DMSO-d6
100 MHz): 84.6 (d, C-2), 73.0 (d, C-3), 198.2 (s, C-4), pound
J
= 11.1 Hz, H-2), 4.91 (1H, d,
J
= 11.1 Hz, (Das et al., 1993) with negative optical rotation ([
= 2.0
16.7o), suggesting that the absolute configuration of
4-(4-hydroxyphenyl)-2-butanol was -form. Thus, com-
was assigned as the 3'-keto derivative of rho-
α]
D
J
= 2.0 Hz, H-6), 5.91 (1H, d,
J
= −
,
R
δ
1

Phenolic Compounds from R. alutaceum
1891
Fig. 1. Chemical structures of 1-15.
3.82 (3H, s, 4''-OCH3)], as well as seven aromatic pro-
tons including two symmetric cones of a tetra-sub-
stituted benzene ring [δH 6.75 (2H, s, H-2', 6')], two
asymmetric cones [
6)], and three ones of a 1,3,4-trisubstituted benzene
ring as an ABX system [ H 6.96 (1H, d, = 2.0 Hz, H-
= 2.0,
δH 6.59 (1H, s, H-4), 6.58 (1H, s, H-
δ
J
2''), 6.72 (1H, d,
J = 8.0 Hz, H-5''), 6.77 (1H, dd, J
8.0 Hz, H-6'')]. Furthermore, the H-1H COSY spec-
1
Fig. 2. Key HMBC Correlations of 1.
trum revealed the presence of three C3 units, Ar-
dodendrin, and named 3'-keto rhododendrin.
CH2CH2CH2OH [
= 0.51, CH3OH), was ob- (2H, m, H-5b), 3.54 (2H, m, H-5c)], Ar-CHCHCH2OH
tained as amorphous powder, and has the molecular H: 5.55 (1H, dd, = 2.1, 5.6 Hz, H-2), 3.43 (1H, m, H-
formula of C30H36O11 as determined by HR-ESI-MS. 3), 3.75, 3.86 (each 1H, m, H-3a)], and Ar-CHCHCH2OH
The IR spectrum of showed absorption bands at H: 4.89 (1H, d, = 4.9 Hz, H-7''), 4.23 (1H, m, H-8''),
3435, 1610, and 1508 cm−1 ascribable to hydroxyl and 3.87, 3.54 (each 1H, m, H-9'')].
δH: 2.56 (2H, t, J = 8.0 Hz, H-5a), 1.78
22
Compound 2, [α]D = − c
4.56o (
[
δ
J
2
[δ
J
aromatic functions.
Comparison of the 1H- and 13C-NMR data of
showed 30 those of dihydrobuddlenol B ( ) (Yoshinari et al., 1990)
2 with
The 13C-NMR and DEPT spectra of
2
5
carbon signals, including three methoxyl groups at δC showed that they were very similar, except for the
1
56.6, 56.6 and 56.3 ppm. The H NMR spectrum of
2
signals of the methoxyl group and the chemical shifts
exhibited three methoxyls [ H 3.79 (6H, s, 3', 5'-OCH3), of H-6, C-6 and C-7 (Table I). HMBC correlations (Fig.
δ

1892
H.-Z. Li et al.
3) from two methoxyls (
(
δ
H 3.79, 6H, s) to C-3' and C-5' 1H-1H COSY, HMQC and HMBC spectra followed by
δC 154.5), and from another methoxyl (δH 3.82, s) to comparison with published 1H- and 13C-NMR data, the
C-4'' (δC 146.4), indicated that above methoxyl groups structure was found to be dihydrobuddlenol B which
were located at C-3', C-5' and C-4'', respectively. No was previously isolated from the bark of Prunus
HMBC correlation observed between any methoxyl jamasakura (Yoshinari et al., 1990). The previously
and C-7, indicated that the methoxyl at C-7 in
replaced by a hydroxyl group in . The C-6 signal of
δC 117.1) was shifted downfield by 3.2 ppm in com- HMBC correlations (Fig. 4) from H-2 (
parison with that of C 113.9), while the signal of C- 6.5 Hz) to C-4a ( C 129.6), from H-4 ( H 6.82, s) to C-5
7 ( C 141.9) of was at a higher field than that of δC C 136.5), and from H-5a ( H 2.56, t, = 7.7 Hz) to C-
C 117.5), C-5 and C-6 ( C 113.9). The above assign-
5
was reported NMR assignments for C-4a, 5, 5a and 5b of
(Table I) required to be revised because of strong
H 5.56, d,
5
2
2
(
δ
J =
5
(δ
δ
δ
δ
2
5
(
(δ
δ
δ
J
144.9), further confirmed that the hydroxyl should be 4 (
δ
assigned to C-7.
ments were further supported by one proton spin
Comparison of the values of the H NMR chemical system from C-5a to C-5c based on H-1H COSY and
1
1
shifts and the coupling constants of H-2, H-3, H-3a, H- HMQC correlations.
7'' and H-8'' with those of related compounds (such as
and acernikol ) suggested that they have the same 2, reported data, others known compounds were identi-
3-cis situation and the 7'', 8''-erythro form (Yoshinari fied as rhododendrin ( ) (Das et al., 1993), ( )-rhodo-
et al., 1990; Agrawal et al., 1983; Agrawal and Thakur, dendrol ( ) (Das et al., 1993), ( )-rhodolatouchol ( ) (Das
1985; Lundgren et al., 1985). In addition, the absolute et al., 1993), ficusequilignan A( ) (Cui et al., 2003),
stereostructure of was determined by circular dichro- ehletianol C ( ) (Yoshikawa et al., 1995), 2,3-dihydro-
ism (CD) spectroscopic analysis. The CD spectrum of benzofuran-2-(4'-hydroxy-3'-methoxyphenyl)-3- -L-
showed a positive Cotton effect at 205 nm and a neg- rhamnopyranosyloxymethyl-7-methoxy-5-propanol (10
ative Cotton effect at 209 nm, indicating the absolute (Marinella and Alessandra, 2004), quercetin 3- -D-
configuration of the 2-position to be in the -orienta- galactopyranoside (11) (Zhang and Tan, 2007), querce-
tion (Morikawa et al., 2003). Thus, the whole stereo- tin 3- -L-arabinofuranoside (12) (Li et al., 2005),
chemistry of was (2, 3-trans-7'', 8''-erythro) 7-demethyl- quercetin (13) (Li et al., 2005), catechin (14) (Wang et
dihydrobuddlenol B and named as alutaceuol. al., 2010a), and myricetin (15) (Zhou et al., 2010), by com-
Compound was assigned the molecular formula of parison of their spectroscopic data with literatures.
C31H38O11 by FAB−MS (m/z 585 [M-H]−) and 13C NMR
Some species of the genus Rhododendron were used
By comparing physical and spectroscopic data with
5
6
3
−
4
−
7
8
2
9
2
α
)
O-β
R
O-α
2
5
spectral data. By interpretation of its 1H-and 13C-NMR, as Chinese traditional medicine for relieving cough
and eliminating phlegm. But among of them maybe
contain grayanane diterpenoids, which can be toxic to
the heart and nervous systems of mammals. In this
work, four 4-(4-hydroxyphenyl)-2-butanol derivatives,
five lignans, and five flavonoids were isolated from R.
alutaceum, while grayanane diterpenoids were undetect-
able. The above research results suggested that R.
alutaceum is non-toxic plant, which could be used as
an herbal medicine.
ACKNOWLEDGEMENTS
Fig. 3. Key HMBC Correlations of 2.
This work was financially supported by the National
Natural Science Foundation of China (20862011,
21062008), the Fok Ying-Tong Education Foundation
(111040), and Specialized Research Fund for the Doc-
toral Program of Higher Education (20095314110001).
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